1. Field of the Invention
The invention is related to an optical microstructure film and a method for fabricating the optical microstructure film, and more particularly to the optical microstructure film applicable to solar cells. The optical microstructure film introduces special microstructures to reduce the formation of gas inside the solar cell so as to improve the yield in mold stripping during the manufacturing of the solar cells.
2. Description of the Prior Art
Referring to FIG. 1, it is shown that an optical film of a conventional solar cell is located tightly between a glass substrate 70 and a back plate 80. During a packaging process in the art, air bubbles or gas voids 90 are opt to be formed between the optical film and the glass substrate 70. Following disadvantages would prevail while meeting the gas voids 90.
1. Possible moisture inside the gas voids 90 on the optical film would lead possible shortcut in electrical elements so as to reduce the photo-electron conversion efficiency.
2. The existence of the gas voids 90 would sponge the optical film and thus reduce its capability in shock-absorbing and anti-impact. As a result, the solar cell is vulnerable to breaks or damages while meeting foreign forcing.
3. Severe delamination would occur among the front panel, the solar cell and the back plate.
To improve the aforesaid shortcomings, some manufacturers are devoted to redesigning the surface structure of the optical film made of the ethylene-vinyl acetate copolymer (EVA). Referring to FIG. 1, protruding microstructures 91 and 92 are formed on the EVA optical film. Gas formed during the packaging process can be expelled out via the ventilation channels provided by the microstructures 90 and 91 during the laminating process of the glass substrate or the solar chip. However, if ventilation channels can't be formed between the microstructures 91 while the gluing resin is in a melted state, the result in gas-expelling would be far from being acceptable. Further, the microstructures 91 can also lead to poor mold delamination upon the EVA optical film and a reduced yield of the EVA optical film 91. Therefore, in order to ensure the yield in mold delamination, a tradeoff in reducing the manufacturing mass scale and increasing the reeling action is inevitable. Thereupon, the production is reduced and a follow-up thermal shrinking problem in the EVA optical film would be met.
In U.S. Pat. No. 7,851,694, an optical film for the conventional solar cells provides a microstructure formed by a plurality of micro protrusions with substantial spacing. However, in this disclosure, the problem in the disappearance of the ventilation channels during the melted state of the gluing material is yet to be resolved.